The skill of sword-fighting is known to two tribes, the Tribes of Light (which consists of humans living on the world’s surface) and Shadow (mostly part humans, part animals or monsters living in an underground city, who also seem to age at half the normal speed of the Light tribe). The two tribes lived in peace and harmony, their domains separated by the “Words Worth” tablet—a huge monolith slab erected by a guardian spirit. Although the tablet has writing on it, neither Tribe can read the text. One day, Words Worth was mysteriously destroyed by an unknown entity; its component parts scattered among the domain of the Tribes of Shadow.

One day while walking home from school, a young college girl is followed by a creepy old man. She runs to a nearby park in an attempt to get away from him, but is captured by someone hiding in the shadows. The pervert strips her naked and mercilessly has his way with her!

Mochidzuki Yuuki and company are cut-off during a trip to an island training camp when civil war erupts. Just as the ship carrying the teachers leave to summon help, it is attacked by unknown persons and sunk.